PORT ANGELES — The public has been warned to avoid contact with Port Angeles Harbor for the next seven days after heavy rains forced about 8 million gallons of stormwater and raw sewage into it.

The Clallam County Environmental Health Division issued the alert Thursday after the city’s four combined sewer overflow, or CSO, outfalls discharged over a four-day period between Sept. 28 and Tuesday.

Two outfalls discharge near the city’s newly completed downtown waterfront esplanade, one sends water into Peabody Creek near where it meets the harbor, and the fourth discharges into the harbor near Francis Street Park.

The discharge could contain fecal bacteria because of the untreated sewage, and contact could result in skin rashes, respiratory infections and other illnesses, according to the county health division.

CSO discharges happen when heavy rains overwhelm the city’s sewer lines, forcing stormwater and sewage into the harbor so they don’t back up into homes, businesses or city streets, according to the city.

The $16.7 million first phase of the city’s CSO project, designed to reduce the amount of CSO discharges into the harbor to about one per year, is expected to be completed by February, said Kathryn Neal, the city’s engineering manager on the project.

The work includes retrofitting a 5 million-gallon storage tank the city bought on the former Rayonier mill property to hold untreated stormwater and sewage during heavy rains until it can be treated in the city’s wastewater-treatment plant near the former mill site.

Both phases of the CSO project, the second of which will upgrade the city’s Marine Drive pump station, are expected to cost a total of $42 million, the largest public works project in city history.

The city is under mandate from the state Department of Ecology to reduce CSO discharges by 2016 or face fines of up to $10,000 for each additional discharge that happens after that deadline.